Rapid determination of letrozole, citalopram and their metabolites by high performance liquid chromatography-fluorescence detection in urine: Method validation and application to real samples

This work reports the validation of a high precision and accuracy method for the simultaneous determination of letrozole, citalopram and their metabolites in urine by high performance liquid chromatography with fluorescence detection. Dilution (urine:mobile phase, 1:2, v/v) was the only sample preparation step. The separation was carried out in a Kromasil C18 (150 mm × 4.6 mm) column, and the mobile phase was phosphate buffer 80 mM (pH 3.0) and acetonitrile (65:35, v/v) at a flow rate of 1.0 mL/min. The analytes were detected at 295 nm after excitation at 230 nm. Linearity was observed in the range of 1.0–1000 ng/mL for letrozole and its metabolite and 2.5–1000 ng/mL for citalopram and their metabolites, with limits of detection and quantification between 0.09–1.0 and 0.27–1.65 ng/mL, respectively. The precisions were satisfactory with RSDs between 0.17 and 5.71%. The accuracy was studied by spiking three urines from healthy female volunteers, and the recoveries were from 85 to 103%. The method was applied to urine samples from women under treatment for breast cancer and depression diseases.